1. Field of the Invention
The present invention relates to an infrared sensor and a method of fabricating the same. More specifically, the present invention relates to an infrared sensor having a sensor structure in which noise characteristics are improved, and a method of fabricating the same.
2. Discussion of Related Art
Basically, an uncooled infrared sensor senses a change in temperature of a sensor by absorbing incident infrared rays. Uncooled infrared sensors are classified into a bolometer type, a pyroelectric type and a thermopile type depending on a method of sensing a change in temperature. The bolometer-type infrared sensor operates by sensing a change in resistance of a sensor resistor according to temperature. Performance of the infrared sensor is ultimately determined by a signal-to-noise ratio, and the noise components mainly consist of Johnson noise and 1/f noise. The Johnson noise is influenced by resistance of a material, and the greater the resistance, the greater the noise. Therefore, in order to reduce the Johnson noise, it is required to design a material constituting the sensor to have a low resistance value. While causes producing the 1/f noise do not clearly appear in theory, the noise is in inverse proportion to frequency. Further, as the volume of the material constituting the sensor becomes greater, the 1/f noise is reduced, and the noise is in proportion to an applied voltage. Therefore, in order to minimize the 1/f noise, it is required to design an electrode structure to maximally utilize the volume of the material, and a portion in which current is non-uniformly supplied such as a cusp should not exist in the sensor.
In the bolometer-type infrared sensor, the most widely used sensing materials include a vanadium oxide (VOx)-based material and an amorphous silicon-based material. In the case of the amorphous silicon-based material, its resistivity is great, and thus when electrodes are simply arranged in parallel, a resistance of the sensor may be too great. As a result, the sensor may have deteriorated characteristics due to Johnson noise caused by the great resistance. In order to overcome the problems, the resistance of the sensor should be lowered, and thus an interdigitated electrode 200 extending from a pad region 110 is used as shown in FIG. 1. However, when the interdigitated electrode 200 is used, there is an inefficiently used portion in a sensing layer 100, and the volume of the sensing layer 100 is inefficiently used. Therefore, there is much room to increase the noise.
Moreover, there is a cusp A vulnerable to the shape of the electrode 200, and non-uniform current around this portion causes 1/f noise to be increased.